A priority-type flow regulator typically has an inlet port, a priority flow port, and a bypass flow port. A priority-type flow regulator can be used to provide a desired priority flow rate regardless of load pressure changes in the priority and bypass lines or of variations in the inlet flow rate.
A combination of a priority flow regulator with a pressure relief valve can be used to provide an additional function—pressure relief of priority flow. In the known priority-flow-with-pressure-relief combination valve arrangements, the pressure relief outlet is connected to the bypass line inside of the valve. In this case, pressure in the bypass line used for auxiliary functions interacts with the pressure in the priority line which can substantially restrict the available pressure level in each of the lines.
Also priority flow regulators and pressure relief valves often are susceptible to instability accompanied by vibration and noise, especially if they are used next to each other. This is so because each of these valves is actually an oscillating system that requires appropriate dampening for stable operation.